The non-fusogenic mammalian orthoreoviruses are members of a family of animal viruses (Reoviridae) that are of considerable importance in human (rotavirus) disease and as oncolytic viruses (reoviruses). Early during reovirus infection small, cytoplasmic, phase-dense inclusions develop which grow in size as infection continues. Viral proteins, as well as partially and fully assembled virions and core particles localize almost exclusively to these structures (termed viral factories) suggesting they are the sites of viral genome replication and assembly. Recently, it has been shown that most viral proteins involved in virus core assembly and genome replication are recruited to the factories through an association with the MNS protein. Moreover, the factories have been found to function as sites for the transcription of viral (+)RNAs, a task that is carried out by core particles, during reovirus infection. This proposal is designed to investigate the role of the reovirus factory in coordinating viral RNA transcription, translation, and replication. The genesis of the viral factory will be investigated to determine at which point in viral infection transcription of viral RNA is located within the protective environment of the factory, and if parental viral core particles direct factory genesis through their association with cellular translation proteins. These experiments will be accomplished by labeling parental cores, then investigating their localization within cells by immunofluorescence, immunoelectron microscopy, and immunoprecipitation studies. Using RNAi technology, the possibility that there are two pools of viral RNA in infected cells, one for replication and one for translation, will be determined. The localization of viral RNA translation and cellular translation factors relative to the localization of viral factories will be examined by immunofluorescence studies to determine if the viral factory, or factory localized proteins direct viral RNA translation. Viral proteins involved in translation will be identified. The role of cis-acting RNA sequences in directing replication within the factory will be investigated by introducing mutations into the viral genome using reverse genetics. These experiments are designed to better understand the role of the viral factory in regulating viral RNA transcription, translation, and replication so that strategies can be developed to interdict and exploit these aspects of reovirus infection. [unreadable] [unreadable]